Various types of analytical tests related to patient diagnosis and therapy can be performed by analysis of a liquid sample taken from a patient's infections, bodily fluids or abscesses. These assays are typically conducted with automated clinical analyzers onto which tubes or vials containing patient samples have been loaded. The analyzer extracts liquid sample from the vial and combines the sample with various reagents in special reaction cuvettes or tubes. Usually the sample-reagent solution is incubated or otherwise processed before being analyzed. Analytical measurements are often performed using a beam of interrogating radiation interacting with the sample-reagent combination to generate turbidimetric, fluorometric, absorption readings or the like. The readings allow determination of end-point or rate values from which an amount of analyte related to the health of the patient may be determined using well-known calibration techniques.
An important contributor to maintaining a high efficiency in throughput of patient samples is the ability to quickly and securely introduce a plurality of samples into the sample testing portion of an analyzer. Patient samples are typically held in a container such as a test tube, and the test tubes placed into a sample rack adapted to support multiple sample containers generally in an upright orientation.
The sample rack is typically placed in an input portion of the analyzer, identified as to type of tube, and moved to a location where a portion of the liquid patient sample is extracted usually by aspiration using a hollow, needle like probe from the tube for testing by the analyzer. Afterwards, the sample rack may be moved to temporary storage area or to an output portion of the analyzer where the user can conveniently remove the sample rack from the analyzer.
Patient samples are known to be provided to such analyzers in a number of different types of tubes. In particular, tubes having 13 mm and 16 mm diameters are popular in a number of different heights and “small sample” tubes, sometimes called small sample cups SSC are typically used for pediatric samples. Sample tube racks have been developed to accommodate different tubes like those described and these racks generally have a vertical opening to enable a bar code reader to read a linear bar code affixed to each tube in order to identify the patient's identity. These markings are generally 1-D, rectilinear and are also provided to assist tracking a tube within the analyzer and to control the mode of aspiration (speed, depth, through-the-stopper or not, and the like). After being placed on the analyzer, a predetermined, known portion of the original sample is aspirated from the tube and analytical tests conducted thereon.
A problem with aspirating a known quantity of sample from a number of different types of tubes arises when different tube types are presented to an aspiration probe or needle. The level of liquid in different tube types varies and the volume of liquid between levels in tubes with different diameters varies. Therefore, when a sample tube is presented to an aspiration probe, in order to aspirate a predetermined, known portion of original sample, the aspiration process must take into account the upper level of liquid, the diameter of the sample tube, as well as the maximum depth available for aspiration.
One solution to this problem requires that an operator place specific size and shape sample tubes in pre-defined slots within a specific sample rack and to ensure that a marking is properly affixed to the tube and oriented in the rack so as to be readable. This requires careful operator attention and introduces a source of error.
U.S. Pat. No. 6,081,326 provides a sample tube carrier especially designed to enable reading of identification codes ascribed on the walls of sample tubes by using a rotary drive to rotate the tube during a code reading process.
U.S. Pat. No. 5,186,339 provides a sample tube rack having similar receptacles with removable base portions and with insertable adapters to accommodate sample tubes of different lengths and diameters. An aperture is formed in the exterior wall to facilitate scanning the containers. U.S. Pat. No. 5,137,693 provides similar adapters to accommodate different size tubes in a test tube holder, the holders having an axial slot for optical viewing of a tube to ascertain its presence. U.S. Pat. No. 5,687,849 also provides moveable collar members to accommodate different diameter tubes in a test tube holder having a viewing slot for observing tubes.
For obvious reasons, it would be highly desirable for an operator to have the freedom to place any tube at any location in a rack and be freed of other restrictions.
From the above descriptions of the art, it is apparent that, while progress has been made in this direction, what has been overlooked is that the small size of some tubes dictates that a “small print” linear marking for identification be used, thereby introducing a large source of error in identifying tube types.